This invention concerns methods of traffic flow management in air traffic control, more particularly, a method for issuing ground delays to flights during air traffic congestion.
The capacity of the major airports to handle arrival flights safely is the major factor that limits the flow of air traffic today in the continental U.S.A. This capacity is fundamentally determined by the available runways and the separation standards imposed between aircraft close to the runway. When the demand on the airport exceeds the capacity for a sustained period of time, arrival aircraft have to be delayed either in the air or on the ground. If delays are unavoidable, it is better to absorb them on the ground due to safety and fuel cost considerations.
The Central Flow Control Facility (CFCF) of the Federal Aviation Administration (FAA) monitors the predicted capacity of the major airports based on weather, maintenance, runway closures, etc., against the anticipated arrival traffic as reflected in the airline schedule, the filed flight plans, and other historic traffic data. This comparison is made everyday usually several hours in advance. If large delays are predicted due to an imbalance between the demand and the anticipated capacity, ground delays are issued to smooth the peaks in demand. The earliest time, after ground delay, at which the aircraft can be cleared for take-off by Air Traffic Control (ATC) is known as the Expected Departure Clearance Time (EDCT). Certain automation aids are available today to the traffic management specialists at the CFCF to make the comparison and issue ground delays.
Uncertainties in the capacity and the demand are inherent to the prediction process. A major factor in the prediction of capacity is the uncertainty associated with the prediction of weather. The demand as reflected in the schedules and flights plans are also unreliable until the flights actually materialize. There may also be unanticipated general aviation, military, and chartered flights. Further, the very process of issuing large ground delays creates uncertainty in the demand, since the flights may cancel or divert to another airport, or may not be able to leave on time because they were delayed elsewhere. The result can be a grossly inefficient utilization of airspace resources; that is, flights can be delayed when the available airport capacity is not being fully utilized.
The present method of issuing ground delays does not make use of dynamic information on flight status. It is based on the assumption that the demand predicted several hours earlier is correct and that the flights will depart according to the assigned departure times. At present, the traffic management specialists have to manually monitor the status of the flights and reissue ground delays as necessary. Hence, it is very difficult to respond effectively to dynamic information that is now available.